The present invention relates to a ball bearing adapted for high speeds, by choice of materials and profiling of the races.
Many measures to make ball bearings suitable for high rotational speeds have been proposed. Hollow balls or ceramic balls are generally known for this purpose. Use of a bearing equipped in this way as a self-aligning bearing is suggested, for example in EP-B 342 172, wherein a bearing has one raceway which is designed to be planar. Relative axial displacement of the raceways can take place without problems in the region of the shoulder-free, planar running surfaces. However, these measures are not sufficient in many applications because of the point contact between the balls and the planar running surface, where it is possible for these parts to wear. This risk is increased if the prestress or radial clearance which is correct for high rotational speeds is not provided. This is because, at too high prestress, the friction and hence the bearing temperature are also impermissibly increased. Self-aligning bearings operable at high rotational speeds are primarily needed in motor spindles.
The object was previously achieved by using spindle bearings which are installed so that they can move axially with respect to a housing. This has the disadvantage that, with a small clearance, operational changes mean that the displaceability is no longer ensured or high displacement forces are needed. This disadvantage is to some extent overcome by specific devices, for example, linear bearings, but with a high expenditure. When cylinder roller bearings are used, the rotational speed is restricted.